Published: March 2026 | By Anitech Occupational Hygiene Team
Part of our Mask Fit Testing Australia: Complete Guide →
The TSI PortaCount Pro+ is the global standard instrument for quantitative respirator fit testing — and it is the method used by Anitech’s fit testing team across Australia. If you work in construction, mining, healthcare, manufacturing or any industry where tight-fitting respirators are mandatory, you will likely encounter a PortaCount test at some point. Understanding how the instrument works, what the results mean, and why quantitative testing provides a stronger compliance record than older subjective methods will help you appreciate the science behind fit testing and the rigor of the protection you are receiving.
This article explains the PortaCount method in plain English, walks through what happens during a test, and shows why this technology is the gold standard in respiratory health effects of DPM protection.
What Is the PortaCount and What Does It Measure?
The PortaCount Pro+ is a portable device about the size of a desktop computer that measures aerosol particle concentrations in real time. CNC stands for Condensation Nuclei Counter — a scientific instrument originally developed for environmental monitoring and now adapted for respirator fit testing.
For workplaces with diesel-powered equipment, understanding diesel particulate matter is an essential part of WHS compliance.
The core principle is deceptively simple: air around you contains thousands of ultra-fine particles — dust, pollen, smoke, sea salt, diesel particulates, bacteria and fungal spores — particles so small they cannot be seen by the naked eye. The PortaCount counts these particles with precision.
During a fit test, the PortaCount takes two simultaneous measurements:
1. Ambient particle count in the air outside the respirator
2. Particle count inside the respirator’s breathing zone (via a tiny sampling tube)
The ratio of these two counts becomes the fit factor — a numerical measure of how well the respirator seals to your face. A fit factor of 200 means that for every 200 particles in the ambient air, only 1 particle penetrates through the seal and reaches your breathing zone. A fit factor of 500 means 1 in 500 penetrates. Higher fit factors = better seals.
This is objective, quantifiable and repeatable — very different from older methods like saccharin or Bitrex tests, which relied on whether a worker could taste a substance.
How the PortaCount Works: The Science Behind the Instrument
Air particles are classified by size in micrometres (µm). The PortaCount measures particles in the ultrafine range: 0.02 to 1 micron — sizes far too small to see under a standard microscope.
When air is drawn into the PortaCount’s optical chamber, it passes through a special region where alcohol vapour condenses around the particles, making them grow to a visible size. A laser beam then detects these enlarged particles. Each particle that passes through the laser triggers a signal, and the instrument counts them — often thousands per second.
The PortaCount’s accuracy and sensitivity is why it is the reference standard for fit testing. Unlike qualitative tests (where a worker says “yes, I taste it” or “no, I don’t”), there is no subjectivity. The particle count is the particle count.
The PortaCount Fit Testing Protocol: What Happens During Your Test
A standard PortaCount fit test follows the protocol specified in AS/NZS ISO 16975-3:2023 — the Australian and New Zealand Standard for fit testing of tight-fitting respiratory protective devices.
Pre-Test Setup (5 minutes)
You will be asked to don the respirator yourself, using the donning method you would use at work. The tester will observe, but will not adjust it for you — they want to see your real-world seal, not an artificially optimised one. A small sampling tube (barely visible) is positioned near your mouth inside the respirator to draw air samples.
The PortaCount is then connected to this tube and powered on. The tester will confirm ambient particle counts are adequate (there must be sufficient ambient aerosol for measurement). If the ambient count is unusually low (e.g. on a very clean day in an indoor office), the tester may use a particle generator to create a stable test aerosol.
The Eight Standard Exercises (60 seconds each)
You will perform the following eight exercises, each lasting approximately 60 seconds. The PortaCount continuously measures particle counts throughout. These exercises are designed to challenge the seal under real-world conditions:
- Normal breathing — Breathe normally and quietly
- Deep breathing — Breathe deeply and slowly, filling your lungs completely
- Head side-to-side — Turn your head left and right (as if saying “no”)
- Head up-and-down — Tilt your head up and down (as if nodding “yes”)
- Talking — Read a standard passage aloud for 60 seconds
- Grimacing — Make exaggerated facial expressions (smile, frown, clench jaw)
- Bending over — Bend at the waist as if touching your toes, then straighten up
- Normal breathing (final) — Resume normal breathing
During each exercise, the PortaCount samples continuously, calculating a fit factor. The overall fit factor for the test is the harmonic mean (a mathematical average weighted towards lower values) of all eight exercise fit factors. This approach ensures that the test is not passed simply because the respirator sealed well during the easy exercises — it must perform adequately across all realistic scenarios.
Test Duration
A complete PortaCount fit test typically takes 15–20 minutes per person, including setup, eight exercises and documentation.
Interpreting PortaCount Results: Fit Factors and Pass/Fail Criteria
Every PortaCount result comes with a numerical fit factor and a pass/fail designation. Here is how to interpret it:
Half-Face Respirator (Dust Masks, Half-Face P2s)
Pass threshold: Fit factor ≥ 100
- Fit factor 100–150: Pass, but the seal is marginal. Any significant change in face shape, facial hair growth, or wearing glasses during work could compromise the fit.
- Fit factor 150–300: Good pass. You are receiving solid protection.
- Fit factor 300+: Excellent pass. The respirator is fitting very well.
Full-Face Respirator
Pass threshold: Fit factor ≥ 500
Full-face respirators are larger and more complex, and therefore expected to achieve higher fit factors. A fit factor of 500 or greater indicates that the full-face seal is performing as intended.
If You Fail
A failure means the overall fit factor is below the threshold (< 100 for half-face, < 500 for full-face). This does not mean you are unsafe — it means that particular respirator model and size is not providing an adequate seal for your face shape.
If you fail a PortaCount test, your tester will:
1. Check your donning technique — sometimes retraining and retesting results in a pass
2. Try alternative models or sizes — different manufacturers and sizes have different geometries that may fit your face better
3. Document the failure and the remedial action in your health monitoring record
4. If no tight-fitting respirator achieves a pass, recommend a powered air-purifying respirator (PAPR) or supplied air respirator (SAR), which do not rely on a face seal
Why Quantitative Testing (PortaCount) Is Superior to Qualitative Testing (Saccharin/Bitrex)
Older qualitative fit test methods (sometimes called QLFT — Qualitative Fit Test) rely on the worker’s sensory perception. In a saccharin test, for example, a worker wears the respirator in a test chamber where saccharin aerosol is present. If they can taste the sweet flavour, they “fail.” If they cannot taste it, they “pass.”
Qualitative tests have significant limitations:
1. Not Everyone Can Taste Saccharin
Approximately 5% of the population is unable to taste saccharin due to genetic variation. These workers cannot undergo a qualitative fit test — they are effectively excluded from a method that should work for everyone.
2. Results Are Subjective
A worker’s answer to “did you taste anything?” depends on their perception, fatigue, attention and willingness to report honestly. One worker might report tasting saccharin at a very low threshold, while another might not report it until the taste is strong. There is no objective benchmark.
3. No Numerical Comparison
A qualitative test result is simply “pass” or “fail.” It doesn’t tell you whether one respirator model is better than another, or whether a worker’s seal has improved with practice. A PortaCount result of 200 is quantifiably better than a fit factor of 110 — both pass, but 200 indicates a more robust seal.
4. Limited to Half-Face Respirators
Qualitative fit testing is technically possible for full-face respirators, but it is unreliable because the eyepieces and other openings complicate the test. Quantitative testing (PortaCount) works equally well for full-face respirators, which is why QNFT is often the only practical option in industries where full-face protection is required (such as underground mining or asbestos removal).
5. No Record of Performance
A qualitative test produces a binary result: pass or fail. In a workers compensation claim or occupational disease investigation, a numerical fit factor is more defensible than a subjective “they passed the taste test.”
What a PortaCount Report Contains
At the end of your fit test, you will receive a detailed report that includes:
- Your name, date of birth and test date
- The tester’s name and RESP-FIT accreditation number
- Respirator model, manufacturer and size
- The fit factor for each of the eight exercises
- Overall fit factor (harmonic mean)
- Pass/fail result
- Any notes or observations
- The next recommended test date
This report is yours to keep, and a copy goes into your employer’s health monitoring records (retained for 30 years, as required by the WHS Regulation).
Common Questions About PortaCount Testing
Does the PortaCount Damage the Respirator?
No. The sampling tube is very small and does not damage the respirator. It is simply a small plastic tube with an internal diameter of a few millimetres. Removing it after the test leaves no mark or defect. The respirator can be used for work immediately after testing.
Is the PortaCount Test Uncomfortable or Painful?
No. The only sensation you may notice is a very slight suction when the sampling tube draws air — so subtle that most workers don’t consciously perceive it. There is no pain, no chemical exposure and no risk of harm. The test is purely non-invasive.
Can I Move Too Much During the Exercises and Invalidate the Test?
The exercises are designed to be challenging — they simulate real-world use. Your job is to perform the exercises as described. If you move excessively or deliberately try to compromise the seal, the tester will note this and may ask you to repeat. But normal movement during the exercises is expected and appropriate.
What If Ambient Particle Counts Are Too Low?
If you are tested in a very clean environment (e.g. a new office building with excellent HVAC), ambient particle counts might be too low for measurement. In this case, the tester can release a controlled test aerosol (a harmless, inert substance) into the air to create a measurable ambient concentration. This is part of standard protocol and does not affect the validity of the result.
Does the PortaCount Work with Beards or Facial Hair?
A tight-fitting respirator cannot seal over facial hair — this is a fundamental principle of respiratory protection. If you have a beard, moustache, or significant stubble, the PortaCount will accurately measure poor fit factors that reflect this reality. Some workers shave specifically for fit testing and work; this is their choice. If you choose not to shave and fail fit testing with tight-fitting masks, PAPR is the appropriate solution.
How Often Do I Need Retesting?
Most employers require annual PortaCount fit tests. Some manufacturers or accreditation standards may require more frequent testing. If your face shape changes significantly (surgery, weight change), you should be retested. If you change employers or are assigned a different respirator model, a new fit test is appropriate.
Related Resources
- AS/NZS ISO 16975-3:2023 – Respiratory protective devices – Fit test procedures Part 3: Quantitative fit test procedures
- TSI PortaCount Pro+ instrument specifications and user manual
- AS/NZS 1715:2009 – Selection, use and maintenance of respiratory protective devices
- RESP-FIT – Accreditation and register for fit testers in Australia
- Safe Work Australia – Guidance on respiratory protective equipment
- Anitech Fit Testing – RESP-FIT accredited PortaCount testing across Australia
Ready for a PortaCount Fit Test?
Anitech provides RESP-FIT accredited PortaCount quantitative fit testing across Australia. Whether you are in construction, mining, healthcare, manufacturing or any industry requiring tight-fitting respirators, our experienced testers will work with you to find a respirator that provides an optimal fit and a strong compliance record.
Book your PortaCount fit test today → or contact our team to discuss fit testing requirements for your workplace.
Anitech Occupational Hygiene Team — delivering quantitative respiratory protection testing across Australia.
